Telescopic jib for jib cranes



Dec. 2, 1.969l

P. EILER TELESCOPIC JIB FOR JIB CRANES Filed June 29, 1967 Illlllflflllllllf IIII l..

United States Patent O 3,481,490 TELESCOPIC .IIB FOR JIB CRANES PeterEiler, Langenfeld, Rhineland, Germany, assignor to Leo Gottwald K.G.,Dusseldorf, Germany Filed June 29, 1967, Ser. No. 649,930 Claimspriority, application Grmany, `lune 30, 1966,

Int. c1. Base 23/06, 23/68 U.S. Cl. 212-55 8 Claims ABSTRACT OF THEDISCLOSURE The invention relates to jib cranes having a telescopic jib.

In existing forms of telescopic jibs', the jib components aremanufactured from rolled sections or welded box structures, which ontheir underside have horizontally disposed running or sliding surfacesfor cooperation with skids or slide shoes carried by the other and lowercomponent. Known constructions are complicated, expensive and haveinadequate guidance of the telescopic components, with static stressingwhich is difficult to assess.

The aim underlying this invention is to provide a telescopicallyextensible and retractable jib for a crane which overcomes thedisadvantages of known jibsI and in which the ratio of useful load todead weight is higher.

According to the invention, in a crane jib of the type set out, byforming at least part of the box sections with bevelled wall portionsthere is provided on the one hand running or guide tracks and on theother hand the supports for rollers or slide shoes which have axesextending parallel to the bevels. This arrangement of the operativesurfaces or guide tracks ensures that the rigidity of the entireconstruction is further increased. In addition, lateral guidance of theinner box is achieved, such as could be obtained in known jibs only withthe aid of additional rollers disposed on the verticals. Satisfactoryresults with improved guidancepperformance of the individual jibcomponents have been obtained where the bevels are at an angle of about45 to the side walls. Furthermore, a crane jib constructed in acocrdancewith the invention has a substantially lower weight than that ofcomparable crane jibs and in the case of slewing cranes this issynonymous with the ability to bear a greater useful load. At the sametime the jib can carry heavier loads, since its jib components consistof a torsionally stii structure'.

According to a further feature of the invention, each box section of thejib is assembled by welding together two sheet metal parts, previouslyfolded into U-form, thereby enabling particularly simple manufacturingmeth ods to be employed. Moreover, those sheet metal parts subjected togreater stresses can -be made of thicker guage sheet than the lessstressed part. Thus, the bottom portion of the box section, which issubjected to compression stressing, can be made of thicker sheet thanthe other portion which is under tension. Crane jibs constructed in thismanner can thus be adapted in an optimum manner to varying loads.

One embodiment of the invention is described and illustrated in thedrawingsI in which:

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FIGURE 1 is a side elevation of a telescopic jib having two telescopingportions according to the invention;

FIGURE 2 is a transverse section on the line II-II of FIGURE l, and

FIGURE 3 is a transverse section on the line III-III of FIGURE 1.

Referring to the drawings, the crane jib consists of two components 1,2, of box-shaped section, which are nested one within the other, .theupper or movable jib com-ponent 1 carrying the head sheave bracket 3being telescopically extensible and retractable in relation to the lowerand static jib component 2, the latter being mounted for luing movementsabout a fulcrum on the slewing base. On the cross-head 3 are guiderollers or pulleys 4 for the lifting ropes 5 or the like. At its innerend the jib component 1 is provided with rollers 6 which engage runningsurfaces 7 (FIGURE 2) on the inside of jib component 2. The rollers 6,as can be seen from FIG- URE l, are mounted on the upper side of theinner end of the moveable component 1, since, when under load, that endis thrust against the top wall of the stationary component 2, as in alever, Iwith the rollers 8 `acting as a fulcrum. The rollers 8 arefastened on the underside of the component 2 and roll on runningsurfaces 9 (FIG- URE 3) provided at the corners and on the outside ofthe underside of the jib component 1.

As can be seen from FIGURES 2 and 3, the job components 1, 2, consist ofbox sections. These box sections may be assembled by uniting two foldedmetal sheets along weld seams 15. Each box section, at least at itsedges, has longitudinally extending bevelled surfaces 7 and 9 with whichsurfaces engage rollers 6 and 8 respectively which are disposed on theother box section in each case. The moveable jib part 1 is constructedat its bottom .bevel with external bearing sur-faces 9, and the jib part2, which is stationary, relative to the jib portion 1, is constructed onthe inside at its upper bevel with internal bearing surfaces 7.

On the other hand the bevels 10, 11 to which are secured the supportbrackets 12, 13 for the rollers 6, 8, need to be provided only at thesections in which the rollers are located.

In order to provide additional stiffening and to accommodate the supportsurfaces 11 for the rollers 8, the stationary jib component 2 has at itsouter end an additional box section 14 which is attached thereto such asby Welding. The roller surfaces 7 and 9 together with the axes of therollers 6 and 8 are preferably inclined by about 45 in relation to theside walls, which has been shown to give good lateral guidance of thejib portions in relation to one another. It also ensures that the sheetsare subjected to minimum stress during folding.

The weld seams v15 in the box sections preferably lie in the neutralfibre, i.e. approximately at the mid-point of the vertical wall, so thatthey are not unduly stressed. In addition, it is possible for foldedsheet metal sections of different thicknesses to be used so that thebottom sheet which is subjected to heavier compressive loads is thickerthan the top sheet where the tensile loads is less. For the purpose oftaking the supporting forces, transverse stiffening webs or plates 16(FIGURE 2) are disposed in the jib component 1 on both sides of therollers 6. In order to ensure uniform loading of the rollers 6, 8, theyare mounted on a rocker. In the embodiment illustrated only two jibsections are shown but clearly the invention is also aplicable wheremore than two jib component's are telescopically displaceable inrelation to one another.

It will be seen that the present invention provides guide surfaces 7, 9,arranged in pairs and respectively 0n each of the box sections 1, 2 orother jib components, these guide surfaces 7, 9 being located upwardlyand downwardly in relation to the longitudinal axis of the jib, theupper pair of surfaces 7 preferably facing inwardly and the faces of thelower pair 9 facing outwardly, for cooperation with thrust rollers orskids similarly arranged in pairs and provided on the other one of eachof the box sections 1, 2. The axes of each pair of rollers and alsotheir associated guide surfaces are at an angle to one another less thana straight angle and preferably such that the guide surfaces are at anangle of 45 or approximately 45 to the sides of the box sections orother components.

What is claimed is:

1. In a jib crane comprising a jib having at least two telescopingcomponents the improvements in which each of said components is providedwith a pair of substantially planar guide surfaces, the surfaces beingangled in relation to one another so that the surfaces of one pair faceinwardly and those of the other face outwardly, said components beingprovided with pairs of thrust elements, one pair of elements in relationto the longitudinal axis of the jib being located on the underside andthe other pair on the upperside of their respective components, saidpairs of elements having faces in slidable engagement respectively withsaid pairs of substantially planar guide surfaces, said faces having awidth smaller than that of said substantially planar guide surfaces, theelements in each pair being spaced laterally and so arranged that theslidably engaging faces thereof extend in planes disposed at an anglecorresponding to the angle at which the respective guide surfaces aredisposed.

2. A jib crane as claimed in claim 1 wherein the guide surfaces extendin planes which are at angles of approximately 90 to one another.

3. In a jib crane comprising a jib having at least two telescopingcomponents, the improvement in which each one of said components isprovided with a pair of substantially planar guide surfaces, thesurfaces being at an angle to one another with respect to thelongitudinal axis of the jib so that the surfaces of one pair faceinwardly and those of the other pair face outwardly, each of saidcomponents being provided with pairs of thrust rollers, one pair ofrollers being located on the underside of one component and the otherpair on the upperside of the other component for cooperationrespectively with said pairs of guide surfaces, said thrust rollershaving peripheral surfaces of a width smaller than that of saidsubstantially planar guide surfaces, and the rollers in each pair beingspaced laterally and being journalled to revolve about axes in atransverse plane, said axes at their point of intersection subtending anangle corresponding to the angle subtended by the guide surfaces.

4. A jib crane as claimed in claim 3 comprising a jib having telescopingcomponents formed of box section members wherein the guide surfaces onthe one member extend in planes which are at an angle of substantially45 to the side walls thereof.

5. A jib crane as claimed in claim 4 wherein each box section member isfabricated from strip metal of U- section assembled end to end andunited by weld seams.

6. A jib crane as claimed in claim 5 wherein the weld seam is located inthe neutral area of the jib.

7. A jib crane as claimed in claim 6 wherein the box section members arefabricated from metal of different thicknesses, that subjected togreater stress being of increased thickness.

8. An extending jib for a crane comprising two telescopically arrangedbox-section members, angled substantially planar guide surfaces on oneof said members and longitudinally spaced pairs of thrust members havingfaces for sliding engagement with said guide surfaces, said faces beingsmaller in width than said substantially planar guide surfaces, aninboard pair of rollers being adjacent the upper sides of said members,and an outboard pair of rollers being adjacent the lower sides of saidmembers, the axes of the rollers being inclined so that the projectedaxes of each pair meet respectively above and below said members, andthe guide surfaces being arranged in planes which are at correspondingangles.

References Cited UNITED STATES PATENTS 2,684,159 7/1954 Olenkamp 212-552,746,612 5/1956` Wirz 212-55 2,817,447 12/1957 Bianca 254-150 2,984,3735/1961 Przybylski 214-141 3,322,206 5/ 1967 Gernhardt 212-55 FOREIGNPATENTS 1,164,334 2/ 1964 Germany.

HARVEY C. HORNSBY, Primary Examiner U.S. C1. X.R. 308-6

